Ambulatory medical device interaction

ABSTRACT

Systems, devices, and techniques that enable medical devices to integrate and interoperate with one another are provided. In some examples, a wearable cardiac defibrillator (WCD) advantageously interoperates with an implanted pacemaker to provide a variety of benefits. For instance, in some examples, the WCD oversees execution of an antitachycardia (ATP) protocol by the implanted pacemaker and intervenes as needed. In other examples, the WCD drives an ATP protocol in which internal pacing pulses are provided by the implanted pacemaker under the control of the WCD. In other examples, the WCD monitors the activity of the implanted pacemaker to identify potential maintenance issues affecting the implanted pacemaker. The WCD and the implanted pacemaker may also interoperate to classify and act upon particular arrhythmia conditions.

RELATED APPLICATION

This application claims the benefit under 35 U.S.C. § 120 as acontinuation of U.S. patent application Ser. No. 15/442,789, titled“AMBULATORY MEDICAL DEVICE INTERACTION,” filed Feb. 27, 2017, thecontent of which is hereby incorporated herein by reference in itsentirety

BACKGROUND

The present disclosure is directed to apparatus and processes throughwhich distinct external and internal or implanted ambulatory medicaldevices may interoperate to monitor and/or treat patients.

There are a wide variety of electronic and mechanical devices formonitoring and treating patients' medical conditions. In some examples,depending on the underlying medical condition being monitored ortreated, medical devices such as cardiac monitors or defibrillators maybe surgically implanted or externally connected to the patient. In somecases, physicians may use medical devices alone or in combination withdrug therapies to treat conditions such as cardiac arrhythmias.

One of the most deadly cardiac arrhythmias include ventricularfibrillation, which occurs when normal, regular electrical impulses arereplaced by irregular and rapid impulses, causing the heart muscle tostop normal contractions and to begin to quiver. Normal blood flowceases, and organ damage or death can result in minutes if normal heartcontractions are not restored. Because the victim has no perceptiblewarning of the impending fibrillation, death often occurs before thenecessary medical assistance can arrive. Other cardiac arrhythmias caninclude excessively slow heart rates known as bradycardia or excessivelyfast heart rates known as tachycardia. Cardiac arrest can occur when apatient in which various arrhythmias of the heart, such as ventricularfibrillation, ventricular tachycardia, pulseless electrical activity(PEA), and asystole (heart stops all electrical activity) result in theheart providing insufficient levels of blood flow to the brain and othervital organs for the support of life.

Cardiac arrest and other cardiac health ailments are a major cause ofdeath worldwide. Various resuscitation efforts aim to maintain thebody's circulatory and respiratory systems during cardiac arrest in anattempt to save the life of the patient. The sooner these resuscitationefforts begin, the better the patient's chances of survival. Implantablecardioverter/defibrillators (ICDs) or external defibrillators, such asmanual defibrillators or automated external defibrillators (AEDs) havesignificantly improved the ability to treat these otherwiselife-threatening conditions. Such devices operate by applying correctiveelectrical pulses directly to the patient's heart. Ventricularfibrillation or ventricular tachycardia can be treated by an implantedor external defibrillator, for example, by providing a therapeutic shockto the heart in an attempt to restore normal rhythm. To treat conditionssuch as bradycardia, an implanted or external pacing device can providepacing stimuli to the patient's heart until intrinsic cardiac electricalactivity returns.

Example external cardiac monitoring and/or treatment devices includecardiac monitors, the ZOLL LifeVest® wearable cardioverter defibrillatoravailable from ZOLL Medical Corporation, and the AED Plus also availablefrom ZOLL Medical Corporation.

SUMMARY

According to one example an ambulatory medical device is provided. Theambulatory medical device includes at least one therapy electrodeconfigured to couple externally to a skin of a patient and to provideone or more transthoracic therapeutic stimulation pulses to a heart ofthe patient; at least one sensing electrode configured to coupleexternally to the skin of the patient and to acquire electrocardiogram(ECG) signals from the patient; and at least one processor coupled tothe at least one therapy electrode and the at least one sensingelectrode. The at least one processor is configured to process the ECGsignals from the patient to detect a tachycardia condition in the heartof the patient; determine, in response to detecting the tachycardiacondition, whether an implanted pacemaker restores the heart of thepatient to a normal condition within a predetermined period; and providethe one or more transthoracic therapeutic stimulation pulses to theheart of the patient in response to determining that the implantedpacemaker failed to restore the heart of the patient to the normalcondition within the predetermined period.

In the ambulatory medical device, the one or more transthoracictherapeutic stimulation pulses may include at least one defibrillationpulse. The at least one processor may be further configured to transmitan alert in response to the implanted pacemaker having failed to restorethe heart of the patient to the normal condition within thepredetermined period. The ambulatory medical device may further includean interface configured to communicate with the implanted pacemaker. Theat least one processor may be further configured to signal the implantedpacemaker to enter an anti-tachycardia pacing (ATP) mode in response todetecting the tachycardia condition. The at least one processor may beconfigured to determine whether the implanted pacemaker restored theheart of the patient to the normal condition at least in part bycomparing the ECG signals to a baseline of the heart of the patientrecorded during an initial fitting of the ambulatory medical device tothe patient. The at least one processor may be configured to determinewhether the implanted pacemaker restored the heart of the patient to thenormal condition at least in part by identifying at least one internalpacing pulse provided by the implanted pacemaker and determining whetherthe at least one internal pacing pulse resulted in myocardialdepolarization.

In the ambulatory medical device, the at least one processor may befurther configured to detect a presence of the implanted pacemakerwithin the patient. The at least one processor may be configured todetect the presence of the implanted pacemaker within the patient atleast in part by processing ECG data representative of the ECG signalsto identify at least one pacing pulse spike. The ambulatory medicaldevice, may further include an electromagnet coupled to the at least oneprocessor. The at least one processor may be configured to detect thepresence of the implanted pacemaker within the patient at least in partby energizing the electromagnet and processing ECG data representativeof the ECG signals to match a heart rate of the patient to at least oneof a magnet rate of the implanted pacemaker, a noise reversion rate ofthe implanted pacemaker, and an interference rate of the implantedpacemaker.

The ambulatory medical device may further include an interfaceconfigured to communicate with the implanted pacemaker. The at least oneprocessor may be further configured to transmit an instruction toreconfigure the implanted pacemaker via the interface in response to theimplanted pacemaker having failed to restore the heart of the patient tothe normal condition within the predetermined period. In the ambulatorymedical device, the instruction to reconfigure may include aninstruction to alter at least one characteristic of at least oneinternal pacing pulse. The at least one characteristic may include atleast one of a pulse waveform, a pulse energy level, a pulse rate, and apulse width.

According to another example, an ambulatory medical device is provided.The ambulatory medical device includes at least one therapy electrodeconfigured to couple externally to a skin of a patient and to provideone or more transthoracic therapeutic stimulation pulses to a heart ofthe patient; at least one sensing electrode configured to coupleexternally to the skin of the patient and to acquire electrocardiogram(ECG) signals from the patient; and at least one processor coupled tothe at least one therapy electrode and the at least one sensingelectrode. The at least one processor is configured to process the ECGsignals from the patient to detect a pattern in the ECG signalsindicative of an arrhythmia condition; monitor the patienttranscutaneously via the at least one sensing electrode for one or moreinternal pacing pulses provided by an implanted pacemaker to the heartof the patient; detect the one or more internal pacing pulses within afirst predetermined time period; and record the pattern as beinguntreatable by the ambulatory medical device within the firstpredetermined time period in response to detecting the one or moreinternal pacing pulses, thereby preventing provision of the one or moretransthoracic therapeutic stimulation pulses.

In the ambulatory medical device, the at least one processor may befurther configured to detect an absence of internal pacing pulses withina second predetermined time period; and record the pattern as beingtreatable within the second predetermined time period in response todetecting the absence of internal pacing pulses. The at least oneprocessor may be further configured to initiate a treatment sequencecomprising providing one or more alerts regarding an impending treatmentto the patient in response to recording the pattern as being treatable.According to another example, an ambulatory medical device is provided.The ambulatory medical device includes at least one therapy electrodeconfigured to couple externally to a skin of a patient and to provideone or more therapeutic stimulation pulses to a heart of the patient; aninterface configured to communicate with an implanted pacemakerimplanted within the patient; and at least one processor coupled to theat least one therapy electrode and the interface. The at least oneprocessor is configured to receive, from the implanted pacemaker via theinterface, atrial ECG data descriptive of atrial heart activity,receive, from the implanted pacemaker via the interface, ventricular ECGdata descriptive of ventricular heart activity, and identify anarrhythmia condition based on the atrial ECG data and the ventricularECG data.

In the ambulatory medical device, the atrial ECG data and theventricular ECG data may indicate atrioventricular dissociation. The atleast one processor may be configured to identify the arrhythmiacondition as a tachycardia condition where the atrial ECG data indicatesa beat rate between 60 beats per minute and 100 beats per minute and theventricular ECG data indicates a beat rate between 110 beats per minuteand 250 beats per minute. The at least one processor may be configuredto determine, in response to detecting the tachycardia condition,whether the implanted pacemaker restored the heart of the patient to anormal condition within a predetermined period and provide the one ormore therapeutic stimulation pulses to the heart of the patient inresponse to determining that the implanted pacemaker failed to restorethe heart of the patient to the normal condition within thepredetermined period. The predetermined period may be 60 seconds. The atleast one processor may be configured to identify the arrhythmiacondition as a fibrillation condition where the atrial ECG dataindicates a beat rate between 60 beats per minute and 100 beats perminute and the ventricular ECG data indicates a beat rate between 300beats per minute and 600 beats per minute; and provide, in response toidentifying the fibrillation condition, the one or more therapeuticstimulation pulses to the heart of the patient via the at least onetherapy electrode. The at least one processor may be configured toidentify the arrhythmia condition as a supraventricular tachycardiacondition where the atrial ECG data indicates a beat rate between 150beats per minute and 250 beats per minute and the ventricular ECG dataindicates a beat rate between 150 beats per minute and 250 beats perminute.

According to another example, an ambulatory medical device is provided.The ambulatory medical device includes a memory storing at least one ECGsignal pattern indicative of at least one associated condition of aninternal cardiac device that requires maintenance of the internalcardiac device; at least one sensing electrode configured to coupleexternally to a skin of a patient and to acquire ECG signals from thepatient; and at least one processor coupled to the memory and the atleast one sensing electrode. The at least one processor is configured toprocess the ECG signals to identify the at least one ECG signal patternswithin the ECG signals; and provide a notification of the at least oneassociated condition to the patient.

In the ambulatory medical device, the at least one ECG signal patternmay include an ECG signal pattern indicating a series of pacing pulsesprovided at a battery pacing rate of the internal cardiac device and theat least one associated condition may include a runtime of a battery ofthe internal cardiac device being below a predetermined value. The atleast one ECG signal pattern may include an indication of a pacing pulsethat failed to result in myocardial depolarization and the at least oneassociated condition may include at least one of lead displacement andwire fracture. The at least one ECG signal pattern may include an ECGsignal pattern lacking a pacing pulse and the at least one associatedconditions may include an oversensing internal cardiac device. The atleast one ECG signal pattern may include an ECG signal patternindicating one or more unnecessary pacing pulses and the at least oneassociated condition may include an undersensing internal cardiacdevice.

According to another example, an ambulatory medical device is provided.The ambulatory medical device includes at least one therapy electrodeconfigured to couple externally to a skin of a patient and to provideone or more subtherapeutic stimulation pulses to a chest wall of thepatient and one or more transthoracic therapeutic stimulation pulses toa heart of the patient; at least one sensing electrode configured tocouple externally to the skin of the patient and to acquire ECG signalsfrom the patient; and at least one processor coupled to the at least onetherapy electrode and the at least one sensing electrode. The at leastone processor is configured to process the ECG signals from the patientto detect a tachycardia condition in the heart of the patient andtrigger an implanted pacemaker to provide one or more internal pacingpulses to the heart of the patient at least in part by providing the oneor more subtherapeutic stimulation pulses to the chest wall of thepatient.

In the ambulatory medical device, the at least one processor may befurther configured to determine whether the implanted pacemaker, inproviding the one or more internal pacing pulses to the heart of thepatient, restored the heart of the patient to a normal condition withina predetermined period and provide the one or more transthoracictherapeutic stimulation pulses to the heart of the patient in responseto determining that the implanted pacemaker failed to restore the heartof the patient to the normal condition within the predetermined period.Each internal pacing pulse of the one or more internal pacing pulses maycorrespond to one subtherapeutic stimulation pulse of the one or moresubtherapeutic stimulation pulses. The at least one processor may befurther configured to determine a tachycardia rate of the tachycardiacondition and trigger the implanted pacemaker to provide the one or moreinternal pacing pulses to the patient at a rate between 80% and 90% ofthe tachycardia rate. The one or more internal pacing pulses may includebetween 5 and 20 internal pacing pulses. The at least one processor maybe further configured to detect a presence of the implanted pacemakerwithin the patient. The at least one processor may be configured todetect the presence of the implanted pacemaker within the patient atleast in part by processing ECG data representative of the ECG signalsto identify at least one pacing pulse spike. The ambulatory medicaldevice may further include an electromagnet coupled to the at least oneprocessor. The at least one processor may be configured to detect thepresence of the implanted pacemaker within the patient at least in partby energizing the electromagnet and processing ECG data representativeof the ECG signals to match a heart rate of the patient to at least oneof a magnet rate of the implanted pacemaker, a noise reversion rate ofthe implanted pacemaker, and an interference rate of the implantedpacemaker.

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects of at least one example are discussed below withreference to the accompanying figures, which are not intended to bedrawn to scale. The figures are included to provide an illustration anda further understanding of the various aspects and examples, and areincorporated in and constitute a part of this specification, but are notintended to limit the scope of the disclosure. The drawings, togetherwith the remainder of the specification, serve to explain principles andoperations of the described and claimed aspects and examples. In thefigures, each identical or nearly identical component that isillustrated in various figures is represented by a like numeral. Forpurposes of clarity, not every component may be labeled in every figure.

FIG. 1 depicts a wearable, ambulatory, external medical device inaccordance with at least one example disclosed herein.

FIG. 2 depicts an arrangement of components of a medical devicecontroller in accordance with at least one example disclosed herein.

FIG. 3 depicts a monitoring and treatment process in accordance with atleast one example disclosed herein.

FIG. 4 depicts another monitoring and treatment process in accordancewith at least one example disclosed herein.

FIG. 5 depicts another monitoring and treatment process in accordancewith at least one example disclosed herein.

FIG. 6 depicts a monitoring process in accordance with at least oneexample disclosed herein.

FIG. 7 depicts another monitoring and treatment process in accordancewith at least one example disclosed herein.

FIG. 8 is a graph illustrating pacing pulse spikes in accordance with atleast one example disclosed herein.

DETAILED DESCRIPTION

This disclosure relates to systems, devices, and techniques thatintegrate the operations of external medical devices with implantablemedical devices. These systems, devices, and techniques may be employed,for instance, by a wearable cardiac defibrillator (WCD) totranscutaneously monitor a patient and a pacemaker implanted within thepatient and in some instances to control the pacemaker. Additionally oralternatively, in some examples, the WCD intervenes to provide therapyto the patient, where the pacemaker is unable to successfully treat thepatient. For example, as noted in detail below, the WCD may interactwith an implantable medical device within a patient in order toinfluence one or more of a pacing mode, multiple rate response settings,electrode polarity, maximum and minimum pacing rates, output energy(e.g., output pulse width and/or output current), sense amplifiersensitivity, refractory periods, calibration information, rate responseattack (e.g., acceleration of rate) and decay (e.g., deceleration orrate), onset detection criteria, and other implanted device parametersettings. For diagnostic purposes, for example, it is also desirable forthe WCD to retrieve from the implanted device information regarding theimplanted device's operational status, which can then be provided to aphysician, technician, or other surrogate.

Pacemakers can detect tachycardia and provide patients withanti-tachycardia pacing (ATP). However, an episode of tachycardia thatis not successfully treated may degrade into atrial fibrillation (AF) orventricular fibrillation (VF). AF and VF are potentially lifethreatening arrhythmias and are conventionally treated by provision ofone or more defibrillating ECG pulses. Implantable cardioverterdefibrillators (ICDs) are capable of providing such defibrillatingpulses, but many traditional pacemakers are not. Thus, a WCD configuredto monitor ATP provided by a traditional pacemaker and defibrillate apatient if needed can save patient lives.

In some examples, a WCD is configured for prophylactic use inconjunction with an implanted pacemaker configured to executeanti-tachycardia pacing. In these examples, the WCD includes may includean electromagnet and use the electromagnet to detect the presence of theimplanted pacemaker. The WCD detects tachycardia conditions suffered bythe patient and monitors the implanted pacemaker and the patient's heartwhile the tachycardia conditions persist. If the WCD determines that theimplanted pacemaker's execution of ATP is not resulting in capture(e.g., myocardial depolarization) or that the patient's heart has notreturned to a normal condition (e.g., normal sinus rhythm) within apredetermined time period, the WCD intervenes by executing any of avariety of preprogrammed actions. Examples of these preprogrammedactions include transmitting one or more notifications to the patient,bystander, or other recipients (including remote recipients), alteringcharacteristics of the ATP pulses, and providing one or moredefibrillation pulses to the patient.

In some examples, a WCD is configured to use pacing pulses issued by animplanted pacemaker to discriminate between true arrhythmias andartifacts that appear to be arrhythmias. For example, when executingaccording to this configuration, the WCD may identify an arrhythmiabased on ECG signals acquired transcutaneously that are, in reality,produced by noise, movement artifacts, or some source other than thepatient's heart. In these situations, an implanted pacemaker may be in abetter position to determine whether a true arrhythmia exists. Toleverage this fact, in some examples a WCD monitors the patient forinternal pacing pulses provided by the implanted pacemaker. Whereinternal pacing pulses are detected, the WCD records the arrhythmia thatit detected as presently untreatable by the WCD. Where internal pacingpulses are not detected, despite the present of the implanted pacemaker,the WCD records the arrhythmia as treatable by the WCD. Where thearrhythmia is treatable, the WCD may execute a treatment sequence, whichmay include provision of alerts to warn the patient or bystander of animpending treatment, and issuance of one or more therapeutic shocks torestore the patient's heart to a normal condition.

In some examples, a WCD is configured to use atrial and ventricularcontraction rates to identify arrhythmias. In these examples, theimplanted pacemaker is a dual chamber pacemaker with both atrial andventricular leads. The implanted pacemaker transmits ECG datadescriptive of atrial and ventricular activity to the WCD. The WCDreceives the ECG data and determines, for example, that an arrhythmia ispresent where the atrial rate is different from the ventricular rate(e.g., where AV dissociation is evident). The WCD may further classifythe arrhythmia as tachycardia (e.g., where the atrial rate is between 60and 100 beats per minute (bpm) and the ventricular rate is between 110and 250 bpm) or fibrillation (e.g., where the atrial rate is between 60and 100 bpm and the ventricular rate is between 300 and 600 bpm). TheWCD may also classify the arrhythmia as supraventricular tachycardiawhere AV dissociation is not evident (e.g., where the atrial rate andthe ventricular rate are each between 150 and 250 bpm). Further in theseexamples, the WCD may supplement the pacemaker by providing one or morepacing pulses where the patient's heart does not return to a normalcondition within a predetermined period of time. The WCD may alsoprovide one or more defibrillation pulses where a fibrillation conditionis detected.

In some examples, a WCD is configured to monitor a patient's cardiacactivity and to drive ATP pacing pulses provided by an implantedpacemaker. When executing according to some of these configurations, theWCD processes ECG signals acquired transcutaneously from the patient todetect arrhythmias and provides a subtherapeutic stimulation pulse tothe chest wall of the patient for each pacing pulse to be provided bythe implanted pacemaker. In some examples, each subtherapeuticstimulation pulse can have a duration in a range of about 25-60milliseconds. In one implementation, a subtherapeutic stimulation pulsehas a duration of approximately 40 milliseconds, a rectangular waveform,and a current within an approximate range of 1 to 50 milliamps. In otherimplementations, subtherapeutic stimulation pulses can have waveformsother than a rectangular waveform, e.g., waveforms where there may be apredetermined amount of a leading or falling slope to the shape of thepulse. The implanted pacemaker, which may be operating in triggeredmode, detects each subtherapeutic stimulation pulse and, in response toeach, provides a corresponding internal pacing pulse. The WCD may beconfigured to detect the presence of the implanted pacemaker and mayinclude an electromagnet for this purpose. The WCD may also providetherapeutic stimulation pulses to the heart of the patient where theimplanted pacemaker is unable to restore the patient's heart to a normalcondition with a predetermined time period.

In some examples, a WCD or an MCT device is configured to monitor ICDoperation for potential maintenance issues with the ICD. In theseexamples, the WCD or MCT device acquires ECG signals from a patient withan ICD and compares the acquired signals to a set of signal benchmarksthat indicate conditions of an ICD that are addressable by maintenanceof the ICD. Examples of these maintenance conditions include a lowbattery, ineffective pacing pulses, omission of needed pulses, andprovision of unneeded pulses. In some examples, the WCD or MCT mayattempt to remediate the maintenance conditions by reconfiguring theICD. For example, the WCD or MCT may adjust the characteristics ofineffective pacing pulses and pacing pulses provided by a ICD with a lowbattery.

The systems, devices, and techniques disclosed herein provide severaladvantages over conventional technology. For instance, some examplesenable pacemakers incapable of providing defibrillating pulses to safelyprovide ATP to patients experiencing tachycardia. In some examples, aWCD can avoid unnecessary transcutaneous pulses by monitoring theactivity of an implanted pacemaker, thereby avoiding patient discomfort.In some examples, a WCD receives enhanced cardiac data from a dualchambered implanted pacemaker, thereby gaining additional insight into apatient condition. In these examples, the WCD may more appropriatelyprovide or withhold therapy based on the enhanced cardiac data. Theenhanced cardiac data can be transmitted to a remote server for furtherreview and analysis, and, in some cases, technicians may use the dataand the remote server to prepare reports that may be delivered tophysicians within a network.

In some examples, a WCD can interoperate with an implanted pacemaker todrive the pacemaker's operation, which can be particular beneficialwhere the implanted pacemaker is operating in an anomalous manner. Insome examples, a WCD monitors the operation of an implanted pacemaker todetect present or potential issues that require maintenance and tonotify a predetermined targeted recipient (e.g., technical supportpersonnel, caregiver, a relative, or a patient surrogate) of the presentor potential maintenance issues. These and other functions of medicaldevices can be enhanced using the systems, devices, and techniquesdisclosed herein.

Example Medical Devices

The teachings of the present disclosure can be generally applied toexternal medical monitoring and/or treatment devices (e.g., devices thatare not completely implanted within the patient's body). Externalmedical devices can include, for example, ambulatory medical devicesthat are capable of and designed for moving with the patient as thepatient goes about his or her daily routine. An example ambulatorymedical device can be a wearable medical device such as a wearablecardioverter defibrillator (WCD), a wearable cardiac monitoring device,an in-hospital device such as an in-hospital wearable defibrillator, ashort-term wearable cardiac monitoring and/or therapeutic device, mobiletelemetry devices, and other similar wearable medical devices.

The wearable medical device is capable of continuous (e.g.,substantially or nearly continuous) use by the patient. In someimplementations, the continuous use may be substantially or nearlycontinuous in nature. That is, the wearable medical device may becontinuously used, except for sporadic periods during which the usetemporarily ceases (e.g., while the patient bathes, while the patient isrefit with a new and/or a different garment, while the battery ischarged/changed, while the garment is laundered, etc.). Suchsubstantially or nearly continuous use as described herein maynonetheless qualify as continuous use. For example, the wearable medicaldevice can be configured to be worn by a patient for as many as 24 hoursa day. In some implementations, the patient may remove the wearablemedical device for a short portion of the day (e.g., for half an hour tobathe).

Further, the wearable medical device can be configured as a long term orextended use medical device. Such devices can be configured to be usedby the patient for an extended period of several days, weeks, months, oreven years. In some examples, the wearable medical device can be used bya patient for an extended period of at least one week. In some examples,the wearable medical device can be used by a patient for an extendedperiod of at least 30 days. In some examples, the wearable medicaldevice can be used by a patient for an extended period of at least onemonth. In some examples, the wearable medical device can be used by apatient for an extended period of at least two months. In some examples,the wearable medical device can be used by a patient for an extendedperiod of at least three months. In some examples, the wearable medicaldevice can be used by a patient for an extended period of at least sixmonths. In some examples, the wearable medical device can be used by apatient for an extended period of at least one year. In someimplementations, the extended use can be uninterrupted until a physicianor other caregiver provides specific instruction to the patient to stopuse of the wearable medical device.

Regardless of the extended period of wear, the use of the wearablemedical device can include continuous or nearly continuous wear by thepatient as described above. For example, the continuous use can includecontinuous wear or attachment of the wearable medical device to thepatient, e.g., through one or more of the electrodes as describedherein, during both periods of monitoring and periods when the devicemay not be monitoring the patient but is otherwise still worn by orotherwise attached to the patient. The wearable medical device can beconfigured to continuously monitor the patient for cardiac-relatedinformation (e.g., ECG information, including arrhythmia information,heart sounds, etc.) and/or non-cardiac information (e.g., blood oxygen,the patient's temperature, glucose levels, tissue fluid levels, and/orlung sounds). The wearable medical device can carry out its monitoringin periodic or aperiodic time intervals or times. For example, themonitoring during intervals or times can be triggered by a user actionor another event.

As noted above, the wearable medical device can be configured to monitorother physiologic parameters of the patient in addition to cardiacrelated parameters. For example, the wearable medical device can beconfigured to monitor, for example, lung sounds (e.g., using microphonesand/or accelerometers), breath sounds, sleep related parameters (e.g.,snoring, sleep apnea), tissue fluids (e.g., using radio-frequencytransmitters and sensors), among others.

Other example wearable medical devices include automated cardiacmonitors and/or defibrillators for use in certain specialized conditionsand/or environments such as in combat zones or within emergencyvehicles. Such devices can be configured so that they can be usedimmediately (or substantially immediately) in a life-saving emergency.In some examples, the wearable medical devices described herein can bepacing-enabled, e.g., capable of providing therapeutic pacing pulses tothe patient.

In implementations, an example therapeutic medical device can include anin-hospital continuous monitoring defibrillator and/or pacing device,for example, an in-hospital wearable defibrillator. In such an example,the electrodes can be adhesively attached to the patient's skin. Forexample, the electrodes can include disposable adhesive electrodes. Forexample, the electrodes can include sensing and therapy componentsdisposed on separate sensing and therapy electrode adhesive patches. Insome implementations, both sensing and therapy components can beintegrated and disposed on a same electrode adhesive patch that is thenattached to the patient. In an example implementation, the electrodescan include a front adhesively attachable therapy electrode, a backadhesively attachable therapy electrode, and a plurality of adhesivelyattachable sensing electrodes. For example, the front adhesivelyattachable therapy electrode attaches to the front of the patient'storso to deliver pacing or defibrillating therapy. Similarly, the backadhesively attachable therapy electrode attaches to the back of thepatient's torso. In an example scenario, at least three ECG adhesivelyattachable sensing electrodes can be attached to at least above thepatient's chest near the right arm, above the patient's chest near theleft arm, and towards the bottom of the patient's chest in a mannerprescribed by a trained professional.

A patient being monitored by an in-hospital defibrillator and/or pacingdevice may be confined to a hospital bed or room for a significantamount of time (e.g., 90% or more of the patient's stay in thehospital). As a result, a user interface can be configured to interactwith a user other than the patient, e.g., a nurse, for device-relatedfunctions such as initial device baselining, setting and adjustingpatient parameters, and changing the device batteries.

In implementations, an example of a therapeutic medical device caninclude a short-term continuous monitoring defibrillator and/or pacingdevice, for example, a short-term outpatient wearable defibrillator. Forexample, such a short-term outpatient wearable defibrillator can beprescribed by a physician for patients presenting with syncope. Awearable defibrillator can be configured to monitor patients presentingwith syncope by, e.g., analyzing the patient's cardiac activity foraberrant patterns that can indicate abnormal physiological function. Forexample, such aberrant patterns can occur prior to, during, or after theonset of symptoms. In such an example implementation of the short-termwearable defibrillator, the electrode assembly can be adhesivelyattached to the patient's skin and have a similar configuration as thein-hospital defibrillator described above.

In some implementations, the medical device may be a patient monitoringdevice with no treatment or therapy functions. For example, such apatient monitoring device can include a cardiac monitoring device or acardiac monitor that is configured to monitor one or more cardiacphysiological parameters of a patient, e.g., for remotely monitoringand/or diagnosing a condition of the patient. For example, such cardiacphysiological parameters may include a patient's electrocardiogram (ECG)information, heart sounds (e.g., using accelerometers or microphones),and other related cardiac information. A cardiac monitoring device is aportable device that the patient can carry around as he or she goesabout their daily routine. The cardiac monitor may be configured todetect the patient's ECG through a plurality of cardiac sensingelectrodes. For example, a cardiac monitor may be attached to a patientvia at least three adhesive cardiac sensing electrodes disposed aboutthe patient's torso. Such cardiac monitors are used in mobile cardiactelemetry (MCT) and/or continuous cardiac event monitoring applications,e.g., in patient populations reporting irregular cardiac symptoms and/orconditions. Example cardiac conditions can include atrial fibrillation,bradycardia, tachycardia, atrio-ventricular block, Lown-Ganong-Levinesyndrome, atrial flutter, sino-atrial node dysfunction, cerebralischemia, syncope, atrial pause, and/or heart palpitations. For example,such patients may be prescribed a cardiac monitor for an extended periodof time, e.g., 10 to 30 days, or more. In some mobile cardiac telemetryapplications, a portable cardiac monitor can be configured tosubstantially continuously monitor the patient for a cardiac anomaly,and when such an anomaly is detected, the monitor may automatically senddata relating to the anomaly to a remote server. The remote server maybe located within a 24-hour manned monitoring center, where the data isinterpreted by qualified, cardiac-trained reviewers and/or caregivers,and feedback provided to the patient and/or a designated caregiver viadetailed periodic or event-triggered reports. In certain cardiac eventmonitoring applications, the cardiac monitor is configured to allow thepatient to manually press a button on the cardiac monitor to report asymptom. For example, a patient may report symptoms such as a skippedbeat, shortness of breath, light headedness, racing heart rate, fatigue,fainting, chest discomfort, weakness, dizziness, and/or giddiness. Thecardiac monitor can record predetermined physiologic parameters of thepatient (e.g., ECG information) for a predetermined amount of time(e.g., 1-30 minutes before and 1-30 minutes after a reported symptom).The cardiac monitor can be configured to monitor physiologic parametersof the patient other than cardiac related parameters. For example, thecardiac monitor can be configured to monitor, for example, heart sounds(e.g., using accelerometers or microphones), lung sounds, breath sounds,sleep related parameters (e.g., snoring, sleep apnea), tissue fluids,among others.

Example Wearable Medical Devices

FIG. 1 illustrates an example medical device 100 that is external,ambulatory, and wearable by a patient 102, and configured to use one ormore of the systems, devices, and techniques described herein tointegrate and/or interoperate with an implantable medical device 116,such as a pacemaker, implanted within the patient 102. For example, themedical device 100 can be a non-invasive medical device configured to belocated substantially external to the patient. Such a medical device 100can be, for example, an ambulatory medical device that is capable of anddesigned for moving with the patient as the patient goes about his orher daily routine. For example, the medical device 100 as describedherein can be bodily-attached to the patient such as the LifeVest®wearable cardioverter defibrillator available from ZOLL® MedicalCorporation. Such wearable defibrillators typically are worn nearlycontinuously or substantially continuously for two to three months at atime. During the period of time in which they are worn by the patient,the wearable defibrillator can be configured to continuously orsubstantially continuously monitor the vital signs of the patient and,upon determination that treatment is required, can be configured todeliver one or more therapeutic stimulation pulses to the patient. Forexample, such therapeutic shocks can be pacing, defibrillation, ortranscutaneous electrical nerve stimulation (TENS) pulses.

The medical device 100 can include one or more of the following: agarment 110, one or more sensing electrodes 112 (e.g., ECG electrodes)one or more therapy electrodes 114, a medical device controller 120, aconnection pod 130, a patient interface pod 140, a belt 150, anelectromagnet 118, or any combination of these. In some examples, atleast some of the components of the medical device 100 can be configuredto be affixed to the garment 110 (or in some examples, permanentlyintegrated into the garment 110), which can be worn about the patient'storso.

The medical device controller 120 can be operatively coupled to thesensing electrodes 112, which can be affixed to the garment 110, e.g.,assembled into the garment 110 or removably attached to the garment,e.g., using hook and loop fasteners. In some implementations, thesensing electrodes 112 can be permanently integrated into the garment110. The medical device controller 120 can be operatively coupled to thetherapy electrodes 114. For example, the therapy electrodes 114 can alsobe assembled into the garment 110, or, in some implementations, thetherapy electrodes 114 can be permanently integrated into the garment110.

Component configurations other than those shown in FIG. 1 are possible.For example, the sensing electrodes 112 can be configured to be attachedat various positions about the body of the patient 102. The sensingelectrodes 112 can be operatively coupled to the medical devicecontroller 120 through the connection pod 130. In some implementations,the sensing electrodes 112 can be adhesively attached to the patient102. In some implementations, the sensing electrodes 112 and therapyelectrodes 114 can be included on a single integrated patch andadhesively applied to the patient's body.

The sensing electrodes 112 can be configured to detect one or morecardiac signals. Examples of such signals include ECG signals and/orother sensed cardiac physiological signals from the patient. In someexamples, the sensing electrodes 112 are included in a housing orcoupled to an assembly that includes additional sensors, such asaccelerometers. In these examples, the sensing electrodes 112 andassociated sensors can also be configured to detect other types ofpatient physiological parameters, such as heart sounds, tissue fluidlevels, lung sounds, respiration sounds, patient movement, etc. Examplesensing electrodes 112 include a metal electrode with an oxide coatingsuch as tantalum pentoxide electrodes, as described in, for example,U.S. Pat. No. 6,253,099 titled “Cardiac Monitoring Electrode Apparatusand Method,” the content of which is incorporate herein by reference.Example sensing electrodes 112 also include conductive electrodes with afoundational layer (e.g., made of foam), an electrically conductiveelement (e.g., made of tin, silver-silver chloride, etc.), and anelectrolytic layer (e.g., made of hydrogel) that electrically couplesthe conductive element to the patient's skin. This electrolytic layermay be applied manually by a healthcare provider or may be disposedautomatically by a gel dispenser positioned near the conductiveelectrode.

In some examples, the therapy electrodes 114 can also be configured toinclude sensors configured to detect ECG signals as well as otherphysiological signals of the patient. The connection pod 130 can, insome examples, include a signal processor configured to amplify, filter,and digitize these cardiac signals prior to transmitting the cardiacsignals to the medical device controller 120. One or more therapyelectrodes 114 can be configured to deliver one or more therapeuticdefibrillating shocks to the body of the patient 102 when the medicaldevice 100 determines that such treatment is warranted based on thesignals detected by the sensing electrodes 112 and processed by themedical device controller 120. Example therapy electrodes 114 caninclude conductive metal electrodes such as stainless steel electrodesthat include, in certain implementations, one or more conductive geldeployment devices configured to deliver conductive gel to the metalelectrode prior to delivery of a therapeutic shock.

In some examples, the electromagnet 118 is coupled to and controllableby the medical device controller 120. In these examples, the medicaldevice controller 120 can energize the electromagnet 118 to cause thepacemaker 116 to enter a default or preprogrammed pacing mode thatdepends on the model of the pacemaker 116. Additionally oralternatively, in some examples, the medical device controller 120 maycommunicate with the pacemaker 116 using other mechanisms, such as radiofrequency or other wireless media.

In some implementations, medical devices as described herein can beconfigured to switch between a therapeutic medical device and amonitoring medical device that is configured to only monitor a patient(e.g., not provide or perform any therapeutic functions). For example,therapeutic components such as the therapy electrodes 114 and associatedcircuitry can be optionally decoupled from (or coupled to) or switchedout of (or switched in to) the medical device. For example, a medicaldevice can have optional therapeutic elements (e.g., defibrillationand/or pacing electrodes, components, and associated circuitry) that areconfigured to operate in a therapeutic mode. The optional therapeuticelements can be physically decoupled from the medical device as a meansto convert the therapeutic medical device into a monitoring medicaldevice for a specific use (e.g., for operating in a monitoring-onlymode) or a patient. Alternatively, the optional therapeutic elements canbe deactivated (e.g., by means or a physical or a software switch),essentially rendering the therapeutic medical device as a monitoringmedical device for a specific physiologic purpose or a particularpatient. As an example of a software switch, an authorized person canaccess a protected user interface of the medical device and select apreconfigured option or perform some other user action via the userinterface to deactivate the therapeutic elements of the medical device100.

WMD/WCD Controller Description

FIG. 2 illustrates a sample component-level view of the medical devicecontroller 120. As shown in FIG. 2, the medical device controller 120can include a therapy delivery circuit 202, a data storage 204, anetwork interface 206, a user interface 208, at least one battery 210, asensor interface 212, a pacemaker interface 228, an cardiac monitor 214,a treatment controller 216, and least one processor 218. A patientmonitoring medical device can include a medical device controller 120that includes like components as those described above, but does notinclude the therapy delivery circuit 202 (shown in dotted lines).

The therapy delivery circuit 202 can be coupled to one or moreelectrodes 220 configured to provide therapy to the patient (e.g.,therapy electrodes 114 a-b as described above in connection with FIG.1). For example, the therapy delivery circuit 202 can include, or beoperably connected to, circuitry components that are configured togenerate and provide the therapeutic electrical pulse or shock. Thecircuitry components can include, for example, resistors, capacitors,relays and/or switches, electrical bridges such as an h-bridge (e.g.,including a plurality of insulated gate bipolar transistors or IGBTs),voltage and/or current measuring components, and other similar circuitrycomponents arranged and connected such that the circuitry componentswork in concert with the therapy delivery circuit and under control ofone or more processors (e.g., processor 218) to provide, for example,one or more pacing or defibrillation therapeutic pulses.

Pacing pulses can be used to treat cardiac arrhythmias such asbradycardia (e.g., less than 30 beats per minute) and tachycardia (e.g.,more than 150 beats per minute) using, for example, fixed rate pacing,demand pacing, anti-tachycardia pacing, and the like. Defibrillationpulses can be used to treat ventricular tachycardia and/or ventricularfibrillation.

The capacitors can include a parallel-connected capacitor bankconsisting of a plurality of capacitors (e.g., two, three, four or morecapacitors). These capacitors can be switched into a series connectionduring discharge for a defibrillation pulse. For example, fourcapacitors of approximately 650 uF can be used. The capacitors can havebetween 350 to 500 volt surge rating and can be charged in approximately15 to 30 seconds from a battery pack, such as the at least one battery210.

For example, each defibrillation pulse can deliver between 60 to 180joules of energy. In some implementations, the defibrillating pulse canbe a biphasic truncated exponential waveform, whereby the signal canswitch between a positive and a negative portion (e.g., chargedirections). This type of waveform can be effective at defibrillatingpatients at lower energy levels when compared to other types ofdefibrillation pulses (e.g., such as monophasic pulses). For example, anamplitude and a width of the two phases of the energy waveform can beautomatically adjusted to deliver a precise energy amount (e.g., 150joules) regardless of the patient's body impedance. The therapy deliverycircuit 202 can be configured to perform the switching and pulsedelivery operations, e.g., under control of the processor 218. As theenergy is delivered to the patient, the amount of energy being deliveredcan be tracked. For example, the amount of energy can be kept to apredetermined constant value even as the pulse waveform is dynamicallycontrolled based on factors such as the patient's body impedance whichthe pulse is being delivered.

The data storage 204 can include one or more of non-transitory computerreadable media, such as flash memory, solid state memory, magneticmemory, optical memory, cache memory, combinations thereof, and others.The data storage 204 can be configured to store executable instructionsand data used for operation of the medical device controller 120. Incertain implementations, the data storage can include executableinstructions that, when executed, are configured to cause the processor218 to perform one or more functions.

In some examples, the network interface 206 can facilitate thecommunication of information between the medical device controller 120and one or more other devices or entities over a communications network.For example, where the medical device controller 120 is included in anambulatory medical device (such as medical device 100), the networkinterface 206 can be configured to communicate with a remote computingdevice such as a remote server or other similar computing device.

In certain implementations, the user interface 208 can include one ormore physical interface devices such as input devices, output devices,and combination input/output devices and a software stack configured todrive operation of the devices. These user interface elements may rendervisual, audio, and/or tactile content, including content relating tolocation-specific processing. Thus the user interface 208 may receiveinput or provide output, thereby enabling a user to interact with themedical device controller 120.

The medical device controller 120 can also include at least one battery210 configured to provide power to one or more components integrated inthe medical device controller 120. The battery 210 can include arechargeable multi-cell battery pack. In one example implementation, thebattery 210 can include three or more 2200 mAh lithium ion cells thatprovide electrical power to the other device components within themedical device controller 120. For example, the battery 210 can provideits power output in a range of between 20 mA to 1000 mA (e.g., 40 mA)output and can support 24 hours, 48 hours, 72 hours, or more, of runtimebetween charges. In certain implementations, the battery capacity,runtime, and type (e.g., lithium ion, nickel-cadmium, or nickel-metalhydride) can be changed to best fit the specific application of themedical device controller 120.

The sensor interface 212 can be coupled to one or more sensorsconfigured to monitor one or more physiological parameters of thepatient. As shown, the sensors may be coupled to the medical devicecontroller 120 via a wired or wireless connection. The sensors caninclude one or more electrocardiogram (ECG) electrodes 222 (e.g.,similar to sensing electrodes 112 as described above in connection withFIG. 1), heart sounds sensors 224, and tissue fluid monitors 226 (e.g.,based on ultra-wide band radiofrequency devices). As such, the sensorinterface 212 may include amplifiers and analog to digital converters tocondition and digitize signals acquired by the sensors.

The ECG electrodes 222 can monitor a patient's ECG information. Forexample, the ECG electrodes 222 can be conductive and/or dry electrodesconfigured to measure changes in a patient's electrophysiology tomeasure the patient's ECG information. The ECG electrodes 222 cantransmit information descriptive of the ECG signals to the sensorinterface 212 for subsequent analysis.

The heart sounds sensors 224 can detect a patient's heart soundinformation. For example, the heart sounds sensors 224 can be configuredto detect heart sound values including any one or all of S1, S2, S3, andS4. From these heart sound values, certain heart sound metrics may becalculated, including any one or more of electromechanical activationtime (EMAT), percentage of EMAT (% EMAT), systolic dysfunction index(SDI), and left ventricular systolic time (LVST). The heart soundssensors 224 can include an acoustic sensor configured to detect soundsfrom a subject's cardiac system and provide an output signal responsiveto the detected heart sounds. The heart sounds sensors 224 can alsoinclude a multi-channel accelerometer, for example, a three channelaccelerometer configured to sense movement in each of three orthogonalaxes such that patient movement/body position can be detected andcorrelated to detected heart sounds information. The heart soundssensors 224 can transmit information descriptive of the heart soundsinformation to the sensor interface 212 for subsequent analysis.

The tissue fluid monitors 226 can use radio frequency (RF) basedtechniques to assess fluid levels and accumulation in a patient's bodytissue. For example, the tissue fluid monitors 226 can be configured tomeasure fluid content in the lungs, typically for diagnosis andfollow-up of pulmonary edema or lung congestion in heart failurepatients. The tissue fluid monitors 226 can include one or more antennasconfigured to direct RF waves through a patient's tissue and measureoutput RF signals in response to the waves that have passed through thetissue. In certain implementations, the output RF signals includeparameters indicative of a fluid level in the patient's tissue. Thetissue fluid monitors 226 can transmit information descriptive of thetissue fluid levels to the sensor interface 212 for subsequent analysis.

The sensor interface 212 can be coupled to any one or combination ofsensing electrodes/other sensors to receive other patient dataindicative of patient parameters. Once data from the sensors has beenreceived by the sensor interface 212, the data can be directed by theprocessor 218 to an appropriate component within the medical devicecontroller 120. For example, if heart data is collected by heart soundssensor 224 and transmitted to the sensor interface 212, the sensorinterface 212 can transmit the data to the processor 218 which, in turn,relays the data to the cardiac monitor 214 and/or the treatmentcontroller 216. This data can also be stored on the data storage 204.

The pacemaker interface 228 can be coupled to an electromagnet 230(e.g., the electromagnet 118 of FIG. 1) positioned substantially near orover an implanted medical device 232 (e.g., the implanted medical device116). In some examples, the pacemaker interface 228 can energize theelectromagnet using power from the battery 210 to cause the implantedmedical device 232 to enter a preprogrammed operational mode. Forinstance, where the implanted medical device 232 is a pacemaker, theelectromagnet 118—when energized—causes the pacemaker to enter, forexample, a magnet pacing mode. For example, the pacemaker may respond toan energized electromagnet by switching to, e.g., an asynchronous pacingrate at a preprogrammed atrioventricular (AV) delay and a fixed ratedepending on the manufacturer, device model, and the status of thebattery. For example, a programmed mode DDD may switch to DOO, or aprogrammed mode VVI may switch to VOO, and a programmed mode AAI mayswitch to AOO. If the WCD does not detect any change in the underlyingECG signal of the patient after application of the electromagnet, theWCD can note its inability to detect the pacemaker, log the effort andrelated information, and continue monitoring the patient's cardiac andother physiological signals. For example, the WCD may not detect anychange in pacemaker activity if a pacemaker is absent and/or removed,has a depleted battery (e.g., low battery charge or end of lifebattery), or programmed to ignore the application of a magnet (e.g., St.Jude, Boston Scientific, and/or Biotronik synchronous modes). As shownin FIG. 2, the pacemaker interface 228 can also be coupled to a wirelessantenna to communicate via radio frequency signals (or other signalingmethods) with implanted medical device 232 to configure and/or otherwisecontrol the implanted medical device 232.

According to some examples illustrated by FIG. 2, the cardiac monitor214 is configured to initiate and control monitoring of a patient'scardiac function and identification of arrhythmias experienced by thepatient. When executing according to this configuration, in someexamples, the cardiac monitor 214 detects arrhythmias by scanning ECGdata received from the sensor interface 212 for patterns (e.g. heartrates) indicative of arrhythmias. Responsive to identifying a datapattern indicative of an arrhythmia, the cardiac monitor 214 initiatesthe pacemaker interface 228 and/or the treatment controller 216.According to various examples, to integrate and/or interoperate with theimplanted medical device 232, the cardiac monitor 214 executes varioussub-processes that are described further below with reference to FIGS.3-7.

According to some examples illustrated by FIG. 2, the treatmentcontroller 216 is configured to initiate and control treatment of anarrhythmia identified by the cardiac monitor 214. When executingaccording to this configuration, in some examples, the treatmentcontroller 216 executes a treatment protocol specific to the particularidentified arrhythmia. For instance, the treatment controller 216 mayinteract with the pacemaker interface 218 to treat a patientexperiencing bradycardia or ventricular tachycardia or may pace thepatient via the therapy delivery circuit 202 and therapy electrodes 220.In some examples, the treatment controller additionally or alternativelydefibrillates the patient where the patient is experiencing atrial orventricular fibrillation. In some examples, the treatment controller 216initiates deployment of electrically conductive gel as part of thetreatment protocol. Also, in some examples, the treatment controller 216monitors the reaction of the patient's heart to the treatment protocoland takes further action based on the reaction of the patient's heart.This further action may include altering the treatment protocol,altering the configuration and/or operation of the implanted medicaldevice 232 via the pacemaker interface 228, and/or escalatingnotifications to external parties. According to various examples, tointegrate and/or interoperate with the implanted medical device 232, thetreatment controller 216 executes various sub-processes that aredescribed further below with reference to FIGS. 3-5 and 7.

Both the cardiac monitor 214 and the treatment controller 216 can beimplemented using hardware or a combination of hardware and software.For instance, in some examples, the cardiac monitor 214 and/or thetreatment controller 216 are implemented as software components that arestored within the data storage 204 and executed by the processor 218. Inthis example, the instructions included in the cardiac monitor 214and/or the treatment controller 216 can cause the processor 218 tomonitor for, detect, and treat arrhythmias. In other examples, thecardiac monitor 214 and/or the treatment controller 216 areapplication-specific integrated circuits (ASICs) that are coupled to theprocessor 218 and configured to monitor for, detect, and treatarrhythmias. Thus, examples the cardiac monitor 214 and the treatmentcontroller 216 are not limited to a particular hardware or softwareimplementation.

In some implementations, the processor 218 includes one or moreprocessors (or one or more processor cores) that each are configured toperform a series of instructions that result in manipulated data and/orcontrol the operation of the other components of the medical devicecontroller 120. In some implementations, when executing a specificprocess (e.g., cardiac monitoring, treatment, etc.), the processor 218can be configured to make specific logic-based determinations based oninput data received, and be further configured to provide one or moreoutputs that can be used to control or otherwise inform subsequentprocessing to be carried out by the processor 218 and/or otherprocessors or circuitry with which processor 218 is communicativelycoupled. Thus, the processor 218 reacts to specific input stimulus in aspecific way and generates a corresponding output based on that inputstimulus. In some example cases, the processor 218 can proceed through asequence of logical transitions in which various internal registerstates and/or other bit cell states internal or external to theprocessor 218 may be set to logic high or logic low. As referred toherein, the processor 218 can be configured to execute a function wheresoftware is stored in a data store coupled to the processor 218, thesoftware being configured to cause the processor 218 to proceed througha sequence of various logic decisions that result in the function beingexecuted. The various components that are described herein as beingexecutable by the processor 218 can be implemented in various forms ofspecialized hardware, software, or a combination thereof. For example,the processor can be a digital signal processor (DSP) such as a 24-bitDSP processor. The processor can be a multi-core processor, e.g., havingtwo or more processing cores. The processor can be an Advanced RISCMachine (ARM) processor such as a 32-bit ARM processor. The processorcan execute an embedded operating system, and include services providedby the operating system that can be used for file system manipulation,display & audio generation, basic networking, firewalling, dataencryption and communications.

Device Interaction Features

Medical devices in accord with various examples disclosed herein utilizeone or more of a variety of features to integrate and/or interoperatewith other, distinct medical devices. For instance, with combinedreference to FIGS. 1 and 2, some examples are configured toadvantageously leverage differences in the construction and dispositionof various medical devices to provide a higher, more comprehensive levelof care to a patient than the individual medical devices could providein isolation. When executing according to these configurations in someexamples, a medical device (e.g., the medical device 100, which may be aWCD) operates in a monitoring mode and/or a treatment mode. Whenoperating in the monitoring mode, the medical device uses one or moresensing electrodes to acquire ECG signals from a patient's (e.g., thepatient 102) heart. Also, while operating in the monitoring mode, aprocessor (e.g., the at least one processor 218) of the medical devicereceives, from a sensor interface (e.g., the sensor interface 212),processed ECG data representative of the acquired ECG signals. Theprocessor provides the ECG data to a cardiac monitor (e.g., the cardiacmonitor 214). The cardiac monitor processes the ECG data to monitor thepatient's cardiac function, to detect the presence of an implantablepacemaker (e.g., the pacemaker 116) implanted within the patient, and/orto monitor the effectiveness of the implanted pacemaker. Should thecardiac monitor determine that the patient is experiencing an arrhythmiacondition (e.g., bradycardia, tachycardia, asystole, pulselesselectrical activity, atrial flutter, or erratic heart rate), the medicaldevice shifts into the treatment mode. While operating in the treatmentmode, the processor provides the ECG data to a treatment controller(e.g., the treatment controller 216). The treatment controller monitorsoperation of the implanted pacemaker, interoperates with the implantedpacemaker as needed to treat the patient, and/or executes a treatmentprotocol in which at least one therapy electrode (e.g., the therapyelectrodes 114) of the medical device may provide one or moretherapeutic stimulation pulses to the patient's heart. Also, within thetreatment mode, the treatment controller monitors the patient's heartvia the ECG data for a reaction to the one or more therapeuticstimulation pulses. This reaction may include, for example, one or morecontractions induced by the therapeutic stimulation pulses and/orcontractions induced by internal pacing pulses provided by thepacemaker.

In some examples, the cardiac monitor and the treatment controller areconfigured to oversee attempts by the implanted pacemaker tosuccessfully execute an ATP protocol and to intervene by providingtherapeutic stimulation pulses to the heart of the patient, ifappropriate. Example processes executed by the cardiac monitor and thetreatment controller in accordance with these configurations aredescribed further below with reference to FIG. 3. When executingaccording to these examples, the cardiac monitor monitors ECG data andinitiates execution of the treatment controller in response to detectinga tachycardia condition affecting the patient's heart. The treatmentcontroller, in turn, monitors the activity of the implanted pacemaker todetermine whether the implanted pacemaker successfully restores thepatient's heart to a normal condition within a predetermined time period(e.g., see act 314 illustrated in FIG. 3).

The normal condition of the patient's heart and the duration of thepredetermined time period may be established during an initial fittingof the medical device. For example, the normal condition of thepatient's heart may be recorded as a baseline specific to the patient.In this way, at some examples tailor the monitoring activities tospecific idiosyncrasies of the particular patient and, by comparing thecurrent condition of the patient's heart to the baseline, are betterable to determine whether the ATP protocol executed by the pacemaker wassuccessful. In some examples, the normal condition of the patient'sheart is such that the patient's heart requires some form of regularlypacing by the implanted pacemaker. Thus, in at least some examples, thetreatment controller determines whether the patient's heart is restoredto a normal condition by identifying that at least one internal pacingpulse issued by the implanted pacemaker resulted in myocardialdepolarization. Similarly, the duration of the predetermined time periodmay default to a particular value (e.g., 60 seconds or some other valuebetween 45 and 75 seconds). In some implementations, a caregiver mayspecify or adjust the predetermine time period during the initialfitting based on the medical history of the patient and the patient'scurrent physical condition.

In some examples, where the treatment controller determines that thepatient's heart is not restored to a normal condition within thepredetermined time period, the treatment controller may execute one ormore of several preprogrammed actions. For instance, the treatmentcontroller may issue an alert if the treatment controller determinesthat the implanted pacemaker was unable to restore the patient's heartto a normal condition within the predetermined time period.Alternatively or additionally, the treatment controller may provide oneor more transthoracic therapeutic stimulation pulses to the patient'sheart. The pulses may include one or more defibrillation pulses.

In some examples, the cardiac monitor may determine whether an implantedpacemaker is disposed within the patient using a variety of systems,devices, and techniques. For instance, in some examples, the cardiacmonitor determines whether the patient has an implanted pacemaker byreferring to one or more values of one or more configurable parametersstored in the data storage 204. Values of configurable parameters may beassigned, for example, by a healthcare provider, via a user interface(e.g., the user interface 208) during an initial fitting of the medicaldevice to the patient. Alternatively or additionally, in some examples,the cardiac monitor 214 is configured to search for and detect animplanted pacemaker via a pacemaker interface (e.g., the pacemakerinterface 228). When executing according to this configuration in oneexample, the cardiac monitor energizes an electromagnet (e.g., theelectromagnet 118) proximal to the implanted pacemaker and monitors theECG data for a heart rate that matches the magnet rate, noise reversionrate, or interference rate of one or more pacemakers. In this example,where the heart rate equals one of these target rates for a particularbrand of pacemaker (e.g., St. Jude, Boston Scientific, Medtronic and/orBiotronik brand pacemakers), the cardiac monitor records that particularpacemaker as being implanted within the patient by manipulating thevalues of the configurable parameters.

In some examples, the cardiac monitor may also detect the presence of animplanted pacemaker by analyzing ECG data in search of pacing pulsespikes. FIG. 8 is a graph 800 of ECG data including two pacing pulsespikes 802A and 802B. The cardiac monitor may detect the presence ofpacing pulse spikes such as the pacing pulse spikes 802A and 802B byusing a derivative based slope detector and/or an amplitude thresholdmonitor. In these examples, the cardiac monitor records the presence ofthe implanted pacemaker by, for example, manipulating the values of theconfigurable parameters described above.

In examples where the medical device includes the pacemaker interfacethat includes a radio frequency antenna, or some other wireless transmitand receive device, the treatment controller may be configured to signalthe implanted pacemaker to enter an ATP pacing mode. This signaling makebe programmed to occur prior to other preprogrammed actions and, infact, may be programmed to occur prior to expiration of thepredetermined time period, if the treatment controller detects that thepacemaker does not appear to be executing an ATP protocol despite thecardiac monitors detection of the tachycardia condition. In someexamples, the treatment controller may be additionally or alternativelyconfigured to adjust the pacing mode of the pacemaker and/or thecharacteristics of pacing pulses provided by the pacemaker in responseto expiration of the predetermined time period and failure by thepacemaker to restore the patient's heart to a normal condition. Thecharacteristics of the pacing pulses that may be altered in this wayinclude the pulse waveform, the pulse energy level, the pulse rate, andthe pulse width.

In some examples, the cardiac monitor and the treatment controller areconfigured to monitor the activity of the implanted pacemaker todiscriminate between actual arrhythmia conditions being experienced bythe patient and artifacts that appear to be arrhythmia conditions.Example processes executed by the cardiac monitor and the treatmentcontroller in accordance with these configurations are described furtherbelow with reference to FIG. 4. When executing according to theseexamples, the cardiac monitor processes ECG data to identify patterns inthe ECG data indicative of an arrhythmia condition. In response todetecting the arrhythmia condition, the cardiac monitor initiatesexecution of the treatment controller. The treatment controller monitorsthe ECG data for internal pacing pulses provided by the implantedpacemaker and determines and records that the arrhythmia is actual, butnot currently treatable by the medical device, where such pacing pulsesare present within a predetermined time period (e.g., see act 410illustrated in FIG. 4). The duration of the predetermined time periodmay default to a particular value (e.g., 10 seconds, some other valuebetween 3 and 45 seconds, or between 3 and 60 seconds). A caregiver mayalso specify or adjust the predetermined time period during an initialfitting of the medical device based on the medical history of thepatient and the patient's current physical condition. However, if pacingpulses are not present within the predetermined time period, thetreatment controller records the arrhythmia as suspect, but treatable bythe medical device, and executes an appropriate treatment protocol. Thetreatment protocol may include provision of one or more alerts.

In some examples wherein the implanted pacemaker is a dual chamberpacemaker, the cardiac monitor and the treatment controller areconfigured to receive atrial and ventricular ECG data from the implantedpacemaker via the pacemaker interface and identify an arrhythmia usingthe atrial and ventricular ECG data. Example processes executed by thecardiac monitor and the treatment controller in accordance with theseconfigurations are described further below with reference to FIG. 5.When executing according to these examples, the cardiac monitor uses theenhanced specificity of the ECG data to detect, for example,atrioventricular dissociation. Further, the cardiac monitor uses theatrial and ventricular ECG data to classify detected arrhythmias. Forinstance, in some examples, the cardiac monitor classifies arrhythmiasas tachycardias where the atrial ECG data indicates an atrial beat rateof between 60 and 100 beats per minute (bpm) and the ventricular ECGdata indicates a ventricular beat rate of between 110 and 250 bpm. Insome examples, the cardiac monitor classifies arrhythmias asfibrillations where the atrial ECG data indicates an atrial beat rate ofbetween 60 and 100 bpm and the ventricular ECG data indicates aventricular beat rate of between 300 and 600 bpm. In some examples, thecardiac monitor classifies arrhythmias as supraventricular tachycardiaswhere the atrial ECG data indicates an atrial beat rate of between 150and 250 bpm and the ventricular ECG data indicates a ventricular beatrate of between 150 and 250 bpm. After classifying the arrhythmia, thecardiac monitor initiates execution of the treatment controller.

In some examples, where the cardiac monitor classifies an arrhythmia asa tachycardia, the treatment controller monitors the patient's ECG datato determine whether the pacemaker is able to restore the patient'sheart to a normal condition within a predetermined time period. Theduration of the predetermined time period may default to a particularvalue (e.g., 60 seconds or some other value between 45 and 75 seconds)and may be adjusted by the caregiver during an initial fitting of themedical device based on the medical history of the patient and thepatient's current physical condition. Where the treatment controllerdetermines that the pacemaker is unable to restore the patient's heartto a normal condition within the predetermined time period, thetreatment controller executes a treatment protocol culminating in one ormore therapeutic stimulation pulses to the patient's heart. In someexamples, where the cardiac monitor classifies an arrhythmia as afibrillation, the treatment controller immediately executes a treatmentprotocol culminating in one or more therapeutic stimulation pulses(e.g., defibrillation pulses) to the patient's heart.

In some examples, the cardiac monitor is configured to monitor theactivity of the implanted pacemaker to determine whether the implantedpacemaker is in need of maintenance. Example processes executed by thecardiac monitor in accordance with these configurations are describedfurther below with reference to FIG. 6. When executing according tothese examples, the cardiac monitor processes ECG data to identifypatterns in the ECG data indicative of maintenance conditions. Inresponse to detecting a maintenance condition, the cardiac monitorprovides one or more notifications to one or more recipients. Theserecipients may include the patient, a caregiver, and/or other externalentities such as persons or systems. The maintenance conditions that maybe detected in these examples include maintenance conditions associatedwith remaining runtime of a battery powering the implanted pacemaker(e.g., the runtime being below a predetermined value); maintenanceconditions associated with lead displacement or wire fracture, whichresult in failure of the implanted pacemaker to initiate myocardialdepolarization via internal pacing pulses; maintenance conditionsassociated with oversensing intrinsic heart activity, which result inlack of provision of needed pacing pulses; and maintenance conditionsassociated with undersensing intrinsic heart activity, which result inprovision of unneeded pacing pulses.

In some examples where the implanted pacemaker is configured intriggered mode (e.g., VVT), the cardiac monitor and the treatmentcontroller are configured to drive an implanted pacemaker to execute anATP protocol and to intervene by providing therapeutic stimulationpulses to the heart of the patient, if appropriate. Example processesexecuted by the cardiac monitor and the treatment controller inaccordance with these configurations are described further below withreference to FIG. 7. When executing according to these examples, thecardiac monitor monitors ECG data and initiates execution of thetreatment controller in response to detecting a tachycardia conditionaffecting the patient's heart. The treatment controller, in turn,provides a pulse train of subtherapeutic stimulation pulses to thepatient's chest wall. Because the implanted pacemaker is configured intriggered mode, each of the pulses in the pulse train is detected by theimplanted pacemaker and results in the implanted pacemaker providing acorresponding internal pacing pulse to the patient's heart.

These pulse trains may have varied characteristics. For instance, insome examples, the treatment controller may determine a tachycardia rateof the tachycardia condition detected by the cardiac monitor and mayprovide a pulse train to the chest wall at a rate that is between 80%and 90% of the tachycardia rate. In addition, the treatment controllermay provide a pulse train including between 5 and 20 pulses within thepredetermined time period.

In some examples, where the treatment controller determines that thepatient's heart is not restored to a normal condition within thepredetermined time period, the treatment controller may execute one ormore of several preprogrammed actions. For instance, the treatmentcontroller may issue an alert if the treatment controller determinesthat the implanted pacemaker was unable to restore the patient's heartto a normal condition within the predetermined time period.Alternatively or additionally, the treatment controller may provide oneor more transthoracic therapeutic stimulation pulses to the patient'sheart. The pulses may include one or more defibrillation pulses.

Prophylactic WCD with an Implanted Pacemaker Executing ATP

As explained above, in some examples a WCD is used as a prophylacticmeasure to enable an implanted pacemaker to execute safely an ATPprotocol. In these examples, the cardiac monitor and the treatmentcontroller of the WCD are configured to execute jointly a monitoring andtreatment process 300 illustrated in FIG. 3.

The monitoring and treatment process 300 starts in the act 302 with thecardiac monitor detecting the presence of an implanted pacemaker. Asexplained above, the cardiac monitor may detect the presence of theimplanted pacemaker using a variety of systems, devices, and techniqueswhich include reading one or more values of one or more parametersconfigured during an initial fitting of the WCD and/or interacting withthe implanted pacemaker via the pacemaker interface.

In act 304 the cardiac monitor monitors ECG data representative of ECGsignals acquired by the sensing electrodes of the WCD. In act 306, thecardiac monitor determines whether the ECG data indicates that thepatient is experiencing a tachycardia condition. If so, the cardiacmonitor calls the treatment controller to initiate its execution in act308. If the cardiac monitor does not detect a tachycardia condition inthe act 306, the cardiac monitor returns to the act 304.

In act 310, the treatment controller determines whether the implantedpacemaker is configured to execute an ATP protocol. The treatmentcontroller may make this determination by reading one or more values ofone or more parameters configured during an initial fitting of the WCDand/or interacting with the implanted pacemaker via the pacemakerinterface. If, in the act 310, the treatment controller determines thatthe implanted pacemaker is configured to execute an ATP protocol, thetreatment controller executes act 314. If, in the act 310, the treatmentcontroller determines that the implanted pacemaker is not configured toexecute an ATP protocol, the treatment controller executes the act 312.

In act 312, the treatment controller adjusts the operating mode of theimplanted pacemaker to an ATP mode via the pacemaker interface. In act314, the treatment controller monitors the ECG data over a predeterminedperiod of time (e.g., 60 seconds). This ECG data reflects the patient'sintrinsic cardiac activity and/or internal pacing pulses generated bythe implanted pacemaker. By monitoring the ECG data, the treatmentcontroller can track and record the effectiveness of the implantedpacemaker's execution of the ATP protocol during the predeterminedperiod of time. In act 316, the treatment controller determines whetherthe ECG data indicates that the implanted pacemaker's execution of anATP protocol successfully restored the heart of the patient to a normalcardiac rhythm within the predetermined time period. It is appreciatedthat each patient may have a distinctive, idiosyncratic normal cardiacrhythm. As such, some examples of the treatment controller compare(e.g., via a convolution operation) the ECG data to a baseline recordedfor the patient during an initial fitting of the WCD. If, in the act316, the treatment controller determines that the implanted pacemakersuccessfully restored the patient's heart to a normal condition (i.e., acardiac rhythm that is normal for the patient), the treatment controllerterminates processing. If, in the act 316, the treatment controllerdetermines that the implanted pacemaker did not successfully restore thepatient's heart to a normal condition, the treatment controller executesact 318.

In the act 318, the treatment controller adjusts, via the pacemakerinterface, one or more characteristics of the internal pacing pulses tobe delivered by the implanted pacemaker. The characteristics of theinternal pacing pulses that may be altered in this way include the pulsewaveform, the pulse energy level, the pulse rate, and the pulse width.For example, the treatment controller may increase the pulse energylevel in an attempt to induce myocardial depolarization of the patient'sheart according to a predetermined anti-tachycardia rate.

In act 320, the treatment controller again determines whether the ECGdata indicates that the implanted pacemaker's execution of an ATPprotocol successfully restored the heart of the patient to a normalcardiac rhythm. If, in the act 320, the treatment controller determinesthat the implanted pacemaker successfully restored the patient's heartto a normal condition, the treatment controller terminates processing.If, in the act 320, the treatment controller determines that theimplanted pacemaker did not successfully restore the patient's heart toa normal condition, the treatment controller executes act 322.

In act 322, due to the implanted pacemaker's inability to successfullytreat the patient's tachycardia condition, the treatment controllerexecutes a treatment protocol. For instance, where the patient is stillexperiencing a tachycardia condition, the treatment protocol executed bythe WCD may culminate in an overdrive pacing pulse train and/or one ormore defibrillation pulses. When executing this treatment protocol, thetreatment controller may coordinate and control various components ofthe WCD to provide the treatment to the patient. For example, thetreatment controller may sound an alarm or otherwise notify the patient,bystanders, and/or local or remote caregivers that treatment of thepatient is imminent. If the notifications are not answered in apredetermined manner to delay treatment, the treatment controller nextsignals gel dispensers to dispense electrically conductive gel betweenthe skin of the patient and the therapy electrodes. These gel dispensersmay be housed in therapy pads that also house the therapy electrodes. Inexecuting the treatment protocol, the treatment controller next signalsdischarge circuitry (e.g., the therapy delivery circuit 202) included inthe WCD provide one or more transcutaneous therapeutic stimulationpulses, such as pacing pulses and/or defibrillating shocks, to thepatient's heart via the therapy electrodes.

In act 324, the treatment controller determines whether the ECG dataindicates that the treatment protocol executed in the act 322successfully restored the heart of the patient to a normal cardiacrhythm. If, in the act 324, the treatment controller determines that thetreatment protocol successfully restored the patient's heart to a normalcondition, the treatment controller terminates processing. If, in theact 324, the treatment controller determines that the treatment protocoldid not successfully restore the patient's heart to a normal condition,the treatment controller executes act 326.

In the act 326, the treatment controller determines whether treatment ofthe patient should continue. For example, within the act 326, thetreatment controller may determine whether execution of the treatmentprotocol has continued for longer than a predetermined duration or formore than a predetermined number of cycles. Also, within the act 326,the treatment controller may determine whether the medical device hassufficient resources available to continue execution of the treatmentprotocol (e.g., whether sufficient battery power remains). If, in theact 326, the treatment controller determines that treatment of thepatient should not continue, the treatment controller terminatesprocessing. If, in the act 326, the treatment controller determines thattreatment of the patient should continue, the treatment controllerproceeds to act 328.

In the act 328, the treatment controller determines whether anyadjustments to the treatment protocol should be made. For example,within the act 328, the treatment controller may analyze the ECG data todetermine adjustments to make to the characteristics of therapeuticstimulation pulses provided by the therapy electrode. Thesecharacteristics may include level of current, pulse width, pulse rate,and waveform among other characteristics. Adjustments identified with inthe act 328 may be based on an inability of the treatment protocol tocapture, cardiovert, or defibrillate the patient, and thus may includeincreasing the level of current and/or pulse width. After appropriatelyadjusting the treatment protocol, the treatment controller returns tothe act 322 and continues to treat the patient.

Arrhythmia Classification

As explained above, in some examples a WCD monitors the activity of animplanted pacemaker to classify arrhythmias as either being suspect, buttreatable by the WCD, or actual, but not presently treatable by the WCD.In these examples, the cardiac monitor and the treatment controller ofthe WCD are configured to execute jointly a monitoring and treatmentprocess 400 illustrated in FIG. 4.

The monitoring and treatment process 400 starts in the act 402 with thecardiac monitor detecting the presence of an implanted pacemaker asdescribed above. In act 404, the cardiac monitor monitors ECG datarepresentative of ECG signals acquired by the sensing electrodes of theWCD. In act 406, the cardiac monitor determines whether the ECG dataindicates that the patient is experiencing an arrhythmia. If so, thecardiac monitor calls the treatment controller to initiate its executionin act 408. If the cardiac monitor does not detect an arrhythmia in theact 406, the cardiac monitor returns to the act 404.

In act 410, the treatment controller monitors the ECG data over apredetermined period of time (e.g., 10 seconds). This ECG data reflectsthe patient's intrinsic cardiac activity and/or internal pacing pulsesgenerated by the implanted pacemaker. By monitoring the ECG data, thetreatment controller can determine whether the implanted pacemaker hasdetected an arrhythmia, which increases the likelihood that thearrhythmia detected by the cardiac monitor is an actual arrhythmia. Inact 412, the treatment controller determines whether the ECG dataincludes pacing pulse spikes, as described above with reference to FIG.8. If so, the treatment controller determines that the implantedpacemaker executes act 414. If the treatment controller determines thatthe ECG data does not include pacing pulse spikes, the treatmentcontroller executes act 418.

In the act 414, the treatment controller records the arrhythmia assuspect, but treatable by the WCD. In act 416, the treatment controllerexecutes one or more treatment protocols which may issue various alertsand provide therapeutic stimulation pulses (e.g., pacing and ordefibrillating pulses) as various described herein. These treatmentprotocols may be adjusted and limited as described above with referenceto the acts 324, 326, and 328. In the act 418, the treatment controllerrecords the arrhythmia as actual, but presently untreatable by the WCD.

As explained above, in some examples a WCD interfaces with a dualchamber implanted pacemaker to classify and potentially treat a varietyof arrhythmias. In these examples, the cardiac monitor and the treatmentcontroller of the WCD are configured to execute jointly a monitoring andtreatment process 500 illustrated in FIG. 5.

The monitoring and treatment process 500 starts in the act 502 with thecardiac monitor detecting the presence of an implanted pacemaker asdescribed above. In act 504, the cardiac monitor monitors atrial andventricular ECG data representative of atrial and ventricular ECGsignals acquired by sensing leads of the dual chamber implantedpacemaker. The atrial and ventricular ECG data may be received from thedual chamber implanted pacemaker via the pacemaker interface. In act506, the cardiac monitor determines whether the atrial and ventricularECG data indicates that the patient is experiencing an arrhythmiaclassifies the arrhythmia, if one is present. For example, the cardiacmonitor may classify the arrhythmia as tachycardia where the atrial rateis between 60 and 100 beats per minute (bpm) and the ventricular rate isbetween 110 and 250 bpm. Alternatively, the cardiac monitor may classifythe arrhythmia as fibrillation where the atrial rate is between 60 and100 bpm and the ventricular rate is between 300 and 600 beats perminute. Alternatively, the cardiac monitor may classify the arrhythmiaas supraventricular tachycardia where the atrial rate and theventricular rate are each between 150 and 250 bpm. If, in the act 506,the cardiac monitor detects an arrhythmia, the cardiac monitor calls thetreatment controller to initiate its execution in act 508. If thecardiac monitor does not detect an arrhythmia in the act 506, thecardiac monitor returns to the act 504.

In act 510, the treatment controller monitors the ECG data over apredetermined period of time. The duration of this period of time mayvary based on the type of arrhythmia detected in act 506. For instance,the duration may range from about 3 seconds to about 60 seconds wherethe arrhythmia detected was a fibrillation, may range from about 3seconds to about 120 seconds or more where the arrhythmia detected is atachycardia. Monitoring the patient's ECG for other predetermineddurations may be possible. For example, the treatment controller maycontinue to monitor the patient's ECG data for the duration that anarrhythmia is detected, and stop monitoring when normal sinus rhythm issustained for a predetermined amount of time (e.g., for at least 2minutes, 5 minutes, 10 minutes, or more). These predetermined durationsmay be specified or adjusted by a caregiver during initial fitting ofthe device based on the individual patient's medical history and/orother factors. In act 512, the treatment controller determines whetherthe ECG data indicates that the heart of the patient to has beenrestored to a normal cardiac rhythm within the predetermined timeperiod. It is appreciated that each patient may have a distinctive,idiosyncratic normal cardiac rhythm. As such, some examples of thetreatment controller compare (e.g., via a convolution operation) the ECGdata to a baseline recorded for the patient during an initial fitting ofthe WCD. If, in the act 512, the treatment controller determines thatthe implanted pacemaker successfully restored the patient's heart to anormal condition (i.e., a cardiac rhythm that is normal for thepatient), the treatment controller terminates processing. If, in the act512, the treatment controller determines that the implanted pacemakerdid not successfully restore the patient's heart to a normal condition,the treatment controller executes act 514. In act 514, the treatmentcontroller executes one or more treatment protocols which may issuevarious alerts and provide therapeutic stimulation pulses (e.g., pacingand or defibrillating pulses) as various described herein. Thesetreatment protocols may be adjusted and limited as described above withreference to the acts 324, 326, and 328.

Maintenance Patterns and Notifications

As explained above, in some examples a WCD monitors the activity of animplanted pacemaker to determine whether the implanted pacemaker is inneed of maintenance. In these examples, the cardiac monitor of the WCDis configured to execute a monitoring process 600 illustrated in FIG. 6.

The monitoring process 600 starts in the act 602 with the cardiacmonitor detecting the presence of an implanted pacemaker as describedabove. In act 604, the cardiac monitor monitors ECG data representativeof ECG signals acquired by the sensing electrodes of the WCD. In act606, the cardiac monitor determines whether the ECG data includes apattern matching one of a plurality of predetermined patterns thatindicate the implanted pacemaker requires maintenance. Thesepredetermined patterns may include a train of pacing pulses having arate equal to a low battery rate for the implanted pacemaker,unnecessary pacing pulses, omitted pacing pulses, and pacing pulses thatfail to result in capture (myocardial depolarization). If, in the act506, the cardiac monitor detects one or more of these predetermined,maintenance patterns in the ECG data, the cardiac monitor issues one ormore notifications to one or more recipients in act 608. These one ormore recipients may include the patient, a caregiver, and/or otherexternal entities such as persons or systems. The notification issuedmay include information regarding the required maintenance. For example,where the maintenance pattern identified is a pulse train having a rateequal to a low battery rate of the implanted pacemaker, the notificationmay indicate that the battery of the implanted pacemaker is low onpower. Where the maintenance pattern identified is unnecessary pacingpulses, the notification may indicate that the implanted pacemaker isundersensing intrinsic heart activity. Where the maintenance patternidentified is omitted pacing pulses, the notification may indicate thatthe implanted pacemaker is oversensing intrinsic heart activity. Wherethe maintenance pattern identified is lack of capture, the notificationmay indicate that lead displacement or wire fracture. If the cardiacmonitor does not detect a maintenance pattern in the act 606, thecardiac monitor returns to the act 604.

WCD Using Triggered Mode to Device ATP Via an Implanted Pacemaker

As explained above, in some examples a WCD is drives an implantedpacemaker configured to operate in triggered mode to execute of an ATPprotocol. In these examples, the cardiac monitor and the treatmentcontroller of the WCD are configured to execute jointly a monitoring andtreatment process 700 illustrated in FIG. 7.

The monitoring and treatment process 700 starts in the act 702 with thecardiac monitor detecting the presence of an implanted pacemaker asdescribed above. In act 704 the cardiac monitor monitors ECG datarepresentative of ECG signals acquired by the sensing electrodes of theWCD. In act 706, the cardiac monitor determines whether the ECG dataindicates that the patient is experiencing a tachycardia condition. Ifso, the cardiac monitor calls the treatment controller to initiate itsexecution in act 708. If the cardiac monitor does not detect atachycardia condition in the act 706, the cardiac monitor returns to theact 704.

In act 710, the treatment controller determines whether the implantedpacemaker is configured to operate in a triggered mode. The treatmentcontroller may make this determination by reading one or more values ofone or more parameters configured during an initial fitting of the WCDand/or interacting with the implanted pacemaker via the pacemakerinterface. If, in the act 710, the treatment controller determines thatthe implanted pacemaker is configured to operate in a triggered mode,the treatment controller executes act 714. If, in the act 710, thetreatment controller determines that the implanted pacemaker is notconfigured to operate in a triggered mode, the treatment controllerexecutes the act 712.

In act 712, the treatment controller adjusts the operating the mode ofthe implanted pacemaker to a triggered mode via the pacemaker interface.In act 714, the treatment controller provides one or more subtherapeuticstimulation pulses to the chest wall of the patent via the therapyelectrodes of the WCD. These subtherapeutic stimulation pulse may bedetected by the implanted pacemaker. When operating in triggered mode,the implanted pacemaker issues an internal pacing pulse in response todetecting each subtherapeutic stimulation pulse. In this way, thetreatment controller drives the implanted pacemaker to execute an ATPprotocol. In some examples, the treatment controller determines anantitachycardia pacing rate and issues the one or more subtherapeuticstimulation pulses in accordance with this antitachycardia pacing rate.For instance, the one or more subtherapeutic stimulation pulses mayinclude 5 to 20 pulses (each resulting in an internal pacing pulse)issued at a rate that is between 80% and 90% of the tachycardia rate.

In act 716, the treatment controller determines whether the ECG dataindicates that the implanted pacemaker's execution of an ATP protocolsuccessfully restored the heart of the patient to a normal cardiacrhythm. It is appreciated that each patient may have a distinctive,idiosyncratic normal cardiac rhythm. As such, some examples of thetreatment controller compare (e.g., via a convolution operation) the ECGdata to a baseline recorded for the patient during an initial fitting ofthe WCD. If, in the act 716, the treatment controller determines thatthe implanted pacemaker successfully restored the patient's heart to anormal condition (i.e., a cardiac rhythm that is normal for thepatient), the treatment controller terminates processing. If, in the act716, the treatment controller determines that the implanted pacemakerdid not successfully restore the patient's heart to a normal condition,the treatment controller executes act 718. In the act 718, the treatmentcontroller executes one or more treatment protocols which may issuevarious alerts and provide therapeutic stimulation pulses (e.g., pacingand or defibrillating pulses) as various described herein. Thesetreatment protocols may be adjusted and limited as described above withreference to the acts 324, 326, and 328.

Additional Examples

Several examples incorporate various combinations of the featuresdescribed above to advantageous effect. For instance, in some examples,the arrhythmia classification features described herein may be combinedwith the prophylactic WCD to enable a WCD to both verify that a suspecttachycardia condition is an actual tachycardia condition and to overseethe implanted pacemaker's execution of an ATP protocol. Additionally, itis appreciated that at least some of the features described herein areoptional and may not be present in every example. For instance, someexamples do not attempt to detect the presence of implanted pacemakersor alter the operating modes of implanted pacemakers via a pacemakerinterface.

Although the subject matter contained herein has been described indetail for the purpose of illustration, it is to be understood that suchdetail is solely for that purpose and that the present disclosure is notlimited to the disclosed examples, but, on the contrary, is intended tocover modifications and equivalent arrangements that are within thescope of the appended claims. For example, it is to be understood thatthe present disclosure contemplates that, to the extent possible, one ormore features of any example can be combined with one or more featuresof any other example.

Other examples are within the scope of the description and claims.Additionally, certain functions described above can be implemented usingsoftware, hardware, firmware, hardwiring, or combinations of any ofthese. Features implementing functions can also be physically located atvarious positions, including being distributed such that portions offunctions are implemented at different physical locations.

1.-35. (canceled)
 36. An ambulatory medical device comprising: at leastone therapy electrode configured to couple externally to a skin of apatient and to provide one or more transthoracic therapeutic stimulationpulses to a heart of the patient; at least one sensing electrodeconfigured to couple externally to the skin of the patient and toacquire external electrocardiogram (ECG) signals from the patient; andat least one processor coupled to the at least one therapy electrode andthe at least one sensing electrode and configured to process theexternal ECG signals from the patient to detect a tachycardia conditionin the heart of the patient, determine, in response to detecting thetachycardia condition, whether an implanted cardiac device restores theheart of the patient to a normal cardiac rhythm within a predeterminedperiod, record execution by the implanted cardiac device of ananti-tachycardia pacing (ATP) protocol during the predetermined periodas effective in response to determining that the implanted cardiacdevice restored the heart of the patient to the normal cardiac rhythmwithin the predetermined period, record execution by the implantedcardiac device of the ATP protocol during the predetermined period asineffective in response to determining that the implanted cardiac devicefailed to restore the heart of the patient to the normal cardiac rhythmwithin the predetermined period, and provide the one or moretransthoracic therapeutic stimulation pulses to the heart of the patientin response to determining that the implanted cardiac device failed torestore the heart of the patient to the normal cardiac rhythm within thepredetermined period.
 37. The ambulatory medical device of claim 36,wherein the one or more transthoracic therapeutic stimulation pulsescomprises at least one defibrillation pulse.
 38. The ambulatory medicaldevice of claim 36, wherein the at least one processor is furtherconfigured to transmit an alert in response to the implanted cardiacdevice having failed to restore the heart of the patient to the normalcardiac rhythm within the predetermined period.
 39. The ambulatorymedical device of claim 36, further comprising an interface configuredto communicate with the implanted cardiac device, wherein the at leastone processor is further configured to signal the implanted cardiacdevice to enter an ATP mode in response to detecting the tachycardiacondition.
 40. The ambulatory medical device of claim 36, wherein the atleast one processor is configured to determine whether the implantedcardiac device restored the heart of the patient to the normal cardiacrhythm at least in part by comparing the external ECG signals to abaseline of the heart of the patient recorded during an initial fittingof the ambulatory medical device to the patient.
 41. The ambulatorymedical device of claim 36, wherein the at least one processor isconfigured to determine whether the implanted cardiac device restoredthe heart of the patient to the normal cardiac rhythm at least in partby identifying at least one internal pacing pulse provided by theimplanted cardiac device and determining whether the at least oneinternal pacing pulse resulted in myocardial depolarization.
 42. Theambulatory medical device of claim 36, wherein the at least oneprocessor is further configured to detect a presence of the implantedcardiac device within the patient.
 43. The ambulatory medical device ofclaim 42, wherein the at least one processor is configured to detect thepresence of the implanted cardiac device within the patient at least inpart by processing ECG data representative of the external ECG signalsto identify at least one pacing pulse spike.
 44. The ambulatory medicaldevice of claim 42, further comprising an electromagnet coupled to theat least one processor, wherein the at least one processor is configuredto detect the presence of the implanted cardiac device within thepatient at least in part by energizing the electromagnet and processingECG data representative of the external ECG signals to match a heartrate of the patient to at least one of a magnet rate of the implantedcardiac device, a noise reversion rate of the implanted cardiac device,and an interference rate of the implanted cardiac device.
 45. Theambulatory medical device of claim 36, further comprising an interfaceconfigured to communicate with the implanted cardiac device, wherein theat least one processor is further configured to transmit an instructionto reconfigure the implanted cardiac device via the interface inresponse to the implanted cardiac device having failed to restore theheart of the patient to the normal cardiac rhythm within thepredetermined period.
 46. The ambulatory medical device of claim 45,wherein the instruction to reconfigure comprises an instruction to alterat least one characteristic of at least one internal pacing pulse. 47.The ambulatory medical device of claim 46, wherein the at least onecharacteristic comprises at least one of a pulse waveform, a pulseenergy level, a pulse rate, and a pulse width.
 48. An ambulatory medicaldevice comprising: at least one therapy electrode configured to coupleexternally to a skin of a patient and to provide one or moretransthoracic therapeutic stimulation pulses to a heart of the patient;at least one sensing electrode configured to couple externally to theskin of the patient and to acquire external electrocardiogram (ECG)signals from the patient; and at least one processor coupled to the atleast one therapy electrode and the at least one sensing electrode andconfigured to process the external ECG signals from the patient todetect, via at least one pacing pulse spike in the external ECG signals,presence of a cardiac device implanted within the patient, the at leastone pacing pulse spike being generated by the implanted cardiac device,process the external ECG signals from the patient to detect a pattern inthe external ECG signals indicative of an arrhythmia condition, monitorthe patient transcutaneously via the at least one sensing electrode forone or more pacing pulse spikes generated by the implanted cardiacdevice subsequent to the at least one pacing pulse spike, detect whetherthe one or more pacing pulse spikes occur within a first predeterminedtime period, record the pattern as being untreatable by the ambulatorymedical device within the first predetermined time period in response todetecting that the one or more pacing pulse spikes occur within thefirst predetermined time period, and prevent, automatically in responseto recording the pattern as being untreatable, provision of the one ormore transthoracic therapeutic stimulation pulses.
 49. The ambulatorymedical device of claim 48, wherein the at least one processor isfurther configured to: detect an absence of pacing pulse spikes within asecond predetermined time period; and record the pattern as beingtreatable within the second predetermined time period in response todetecting the absence of pacing pulse spikes.
 50. The ambulatory medicaldevice of claim 49, wherein the at least one processor is furtherconfigured to initiate a treatment sequence comprising providing one ormore alerts regarding an impending treatment to the patient in responseto recording the pattern as being treatable.
 51. The ambulatory medicaldevice of claim 48, wherein the at least one processor is furtherconfigured to detect a presence of the implanted cardiac device withinthe patient.
 52. The ambulatory medical device of claim 51, wherein theat least one processor is configured to detect the presence of theimplanted cardiac device within the patient at least in part byprocessing ECG data representative of the external ECG signals toidentify at least one pacing pulse spike.
 53. The ambulatory medicaldevice of claim 48, further comprising an interface configured tocommunicate with the implanted cardiac device, wherein the at least oneprocessor is further configured to transmit an instruction toreconfigure the implanted cardiac device via the interface in responseto the implanted cardiac device having failed to restore the heart ofthe patient to the normal cardiac rhythm within the predeterminedperiod.
 54. The ambulatory medical device of claim 53, wherein theinstruction to reconfigure comprises an instruction to alter at leastone characteristic of at least one internal pacing pulse.
 55. Theambulatory medical device of claim 54, wherein the at least onecharacteristic comprises at least one of a pulse waveform, a pulseenergy level, a pulse rate, and a pulse width.